The mother of the two British backpackers who survived 18 hours in the Indian Ocean when their boat sank today told of her relief and said she was looking forward to having them home.

Sisters Katherine, 21, and Alice Ostojic, 19, were on a tourist boat in Indonesia when disaster struck.

The pair, along with other passengers, sat on the roof of the boat as it slowly became submerged before jumping into the water and swimming for eight hours until they were rescued by local fishermen.

Today their mother Joan told how her daughters have been in touch by email to let her and her husband Peter, an engineer, know they are safe and well.

Speaking from the family home in Stevenage, Mrs Ostojic, who works in IT, said: “The first we knew of the accident was from the girls and that they were safe but we are still very relieved.

Rescue: Alice Ostojic in a photo on her travels

“The girls are fine but a little sunburnt. They have limited access to email, so we have not been able to get the full story.”

The drama unfolded on Saturday, the second day of a three-day boat trip from to the island of Lombok to Komodo, famous for its dragon lizards. A 10ft wave threw the vessel into a reef and the hull was damaged.

Mrs Ostojic said: “The girls had a lovely time climbing the Rinjani volcano on Lombok, and were on their way to see the Komodo Dragon when the incident happened.

“I’m glad I didn’t know about it beforehand, it means I didn’t have time to worry.”

Safe: Katherine Ostojic

She added: “They are fine, carrying on with their travels and they will be home on the weekend. I’m looking forward to seeing them both and hearing all about it.”

After being plucked from the ocean along with eight other people, they were taken to an uninhabited island where they spent the night and where the fishermen gave them food and water before taking them on to a larger island.

The British Vice-Consul in Indonesia then got the girls flown to Bali, where they will stay until continuing their travels to Sumatra. They managed to keep their passports, debit cards and cash with them but lost everything else.

Katherine Ostojic and her sister Alice with cousin Jack

Alice, who is on a gap year, has spent the last five months travelling through New Zealand, Australia, Thailand, Cambodia, Vietnam and Laos. Her sister, a Bristol University student who is studying Aerospace Engineering joined her for the last month of her travels after completing a summer course in space travel and geophysics in Austria.

Mrs Ostojic added: “The girls are now keen to put pressure on the Indonesian government to raise the safety of their boats. They said there wasn’t even a radio on board.”

A further 13 people, eight foreigners and five Indonesians, were rescued yesterday.

In an email to their parents yesterday, the girls wrote: “They have found everyone now, such a relief. The boat sank in the middle of the night, we sat on it’s roof while it was semi-submerged for 10 hours then swam 8 hours to the shore before seeing the lights of some fishermen and getting them to pick us up.”

Referring to earlier reports, they added: “N.B no urine was drunk and no leaves were eaten, at least not by us...”